DE 10 2004 059 062 A1 discloses a fuel filter comprising water separation in which the separated water sinks into a collecting chamber. A sensor detects the water level and delivers a signal for opening a valve whereupon the pump conveys the water into a water discharge device.
A commercially available fuel filter system of an internal combustion engine of a motor vehicle has a suction line that connects a fuel tank with an inlet of a fuel pump. In the suction line there is a prefilter for filtering the conveyed fuel. Moreover, the fuel filter system has a pressure line that connects an outlet of the fuel pump with a high-pressure pump of the fuel supply system. In the pressure line there is a main filter for the fuel and a water separator for separating water contained in the fuel. The water separator is connected with a water collecting chamber in which the water that has been separated is collected. From the water collecting chamber a water drain line passes into the environment. In the water drain line there is a water discharge valve that can be opened for draining the water. Behind the water discharge valve in the water drain line a ceramic cleaning device with a channel structure is arranged. By means of the ceramic cleaning device hydrocarbons which may be contained in the separated water are removed from the water. The thus purified water can be drained into the environment. The separated hydrocarbons remain within the ceramic cleaning device. In order to ensure permanently an efficient separation of hydrocarbons from the water, the ceramic cleaning device must be exchanged regularly. The service life of the ceramic cleaning device is moreover shortened in that residual water with hydrocarbons remaining in a space between the water discharge valve and the ceramic cleaning device causes soiling of the ceramic cleaning device. Under frost, the residual water can freeze and damage the ceramic cleaning device.
The invention has the object to configure a fuel filter system and a method for separating water of the aforementioned kind in which always an efficient water separation from the fuel and an optimal cleaning of the separated water are ensured. Moreover, the cleaning component should have a service life as long as possible.